Our planets bear the roman names of Gods, as we refer to Jupiter with the name of the roman king of the heavens. However, we call the Sun as such because of old english words, not Helios or Sol. How did the Egyptians refer to the Sun after their Sun God, Ra? Would an ancient Egyptian say something like "Ugh, the clouds are terrible, I haven't seen Ra in a week!" or "I'll be there before Ra sets," or did they have some other word for it?
They did indeed! The god Ra and ra ("sun") are written slightly differently, however, thanks to the Egyptian system of determinatives.
Determinatives are unvocalized hieroglyphs written at the end of a word to disambiguate that word. For example, action verbs often have the striking arm determinative, and male and female names are accompanied the seated man and woman determinative, respectively. Determinatives/classifiers are extremely important because the Egyptian hieroglyphic system – unlike Anatolian or Maya hieroglyphic writing – does not record vowels, so unrelated words can appear very similar. For example, English ct could be read as cat, cut, cot, cute, cite, and so on.
The Egyptians wrote the god Ra as 𓂋𓂝𓇳𓁛 and "sun" as 𓂋𓂝𓇳𓏤.
𓂋 -> uniliteral sign r
𓂝 -> uniliteral sign a
𓇳 -> solar determinative
𓁛 -> seated god determinative
𓏤 -> logographic stroke, which indicates that a hieroglyph is being used to write the word for what it depicts
As a heads up, this sort of question is great for the Short Answers to Simple Questions thread, since there's not a lot to say on this topic.